Systematic Reviews: Related Review Types

Meta-analyses statistically combine the results of studies in a systematic review to provide a more precise effect of the results. Meta-analysis can only be done when all included studies are sufficiently similar. All studies must measure the same outcome in the same way at the same time intervals.

• PRISMA Preferred Reporting Items for Systematic Reviews and Meta-Analyses 

Scoping/Mapping reviews examine a broad topic rather than try to answer a specific question. They identify the nature and extent of existing research in order to:

• identify gaps in the literature to see where future research is needed 
• examine the extent, variety, and characteristics of the evidence on a topic 
• determine if it's feasible to do a systematic review

Like systematic reviews, they require a comprehensive systematic search and structured reporting but they don't assess risk of bias of included studies.

• PRISMA for Scoping Reviews Checklist
• JBI Guidance for Scoping Reviews 
• JBI Templates for Scoping Reviews
• Mapping Review Methods

Systematized reviews only include some elements of the systematic review process. They're usually conducted as post-graduate student assignments in a short time frame. They may not include: 

• systematic comprehensive searching
• quality assessment of selected studies
• a systematic synthesis of the results 

Mixed method reviews are systematic reviews that include both qualitative and quantitative studies. Unlike most systematic reviews which focus only on the effectiveness of an intervention, mixed methods reviews give decision-makers a more complete understanding of complex issues.  They are difficult to conduct because of the heterogeneous nature of the included studies. This complicates the searching, quality assessment, data extraction, and data synthesis. There are several methods of synthesizing the diverse types of studies. 

• JBI Guidance for Mixed Methods
• Cochrane Handbook: Qualitative Evidence 

A typology of reviews: an analysis of 14 review types and associated methodologies

Meeting the review family: exploring review types and associated information retrieval requirements

An umbrella review is a review of reviews. It compiles the evidence from existing reviews, usually systematic reviews and meta-analyses. Umbrella reviews often compare multiple different competing interventions for a condition.   

• Summarizing Systematic Reviews
• Methodology for JBI Umbrella Reviews

Rapid reviews use systematic review methods but set limits on the process in order to complete the review as quickly as possible. They are usually used for emergency decision-making in critical situations such as the Ebola virus outbreak. In order to produce results quickly, they may limit the comprehensiveness of the search or the quality appraisal.  

• Cochrane Rapid Review Methods

• NCCMT Rapid Review Guidebook

Systematic reviews of case reports/series aren't frequently done but sometimes there is no other evidence on a rare disease, new drug, or adverse events. In these cases, you might only have case reports to examine.

Guidelines:

• A Protocol for the Use of Case Reports/Studies and Case Series in Systematic Reviews for Clinical Toxicology             

• Cochrane only gives snippets of advice:

Cochrane Handbook, Ch 24:

“for some rare or delayed adverse outcomes only case series or case-control studies may be available. Non-randomized studies of interventions with some study design features that are more susceptible to bias may be acceptable for evaluation of serious adverse events in the absence of better evidence, but the risk of bias must still be assessed and reported”

Cochrane Systematic Reviews of Adverse Effects: Framework for a Structured Approach. BMC Med Res Methodol. (2007) 7:32. doi: 10.1186/1471-2288-7-32

"The Cochrane Adverse Effects group has shown that case studies may be the best settings in which to observe adverse effects, especially when they are rare and acute."

Evaluation of quality of case reports:

• JBI has a critical appraisal tool for case reports and case series.
• Navigation Guide tool (includes 9 domains of bias; you need to adapt it from an SR which has already used it such as:
  • An evidence-based medicine methodology to bridge the gap between clinical and environmental health sciences.  
  • The Navigation Guide - evidence-based medicine meets environmental health: integration of animal and human evidence for PFOA effects on fetal growth.  
• CARE (CAse REport) ( a checklist for reporting case reports but it could be used to evaluate CRs also).  
• BMJ's Methodological quality and synthesis of case series and case reports.

Registration:

Prospero accepts protocols for SRs of case reports